The conventional safety door, such as a fire door and an emergency door, consists of one or the other of these two types of systems based on the type of door controller, that is, the failsafe system and the non-failsafe system. As the safety door is usually used as a door access system for ordinary people, these two door controller systems both have their merits and demerits in usage depend on the user,
(1 ) Failsafe system: In the case of electricity failure, no matter what the reason is, the braking device of the door controller should immediately release the braking and shut off the safety door. In the event of fire alarm without electricity failure, the brake device will be released by cutting off the power by such device as smoke detector, or temperature sensor, or the other fire alarm detector, or by cutting off the power with a mechanical means after a fusible links is melted in high temperature due to the fire, so that the safety door will close. If the reason of electricity failure is definitely due to the fire, the device can block the pilot fire or the exhaust smoke at the first instant of fire. So, the system is preferred due to its higher safety of fire protection. However, if the electricity failure is not due to fire, the system will cause some inconvenience, and affect normal entry/exit function. This is the major defect. A number of relevant documents has been proposed, for example, the U.S. Pat. Nos. 5,850,865, 5,245,879, 5,893,234, 5,673,514, U.S. Ser. No. 11/489,329, U.S. Ser. No. 11/012,545 and U.S. Ser. No. 10/998,373 etc. belongs to this failsafe system category. In the case of unexpected electricity failure, the brake will actively be released, so the door will close.
(2) Non-failsafe system: In the case of electricity failure, no matter what the reason is, the braking device will come into braked state and not shut off the safety door immediately. After the fire alarm has been confirmed by the device such as smoke detector, temperature sensor or the other fire detecting devices, temporary current is supplied by a back-up power source, such as capacitor or battery, to the brake device so as to temporarily maintain the releasing of the brake, or a fusible links is melted in high temperature under the fire to activate the brake device so as to release the braking by a mechanical means, so the safety door will close on its own. This type of system provides the advantage of not shutting off the safety door immediately after the electricity failure. If electricity failure is not due to fire, the access of the door by user is not affected.
However, the person skilled in the art should understand that if the reason of electricity failure was indeed due to fire, and if the fire location is at a certain distance away from the fire detecting device or the fusible links, the safety door is unable to be shut off at the first instant of fire, in the case a non-failsafe door controller is used. The insufficiency in safety is the main demerit of this type.